Art of cleansing lens mounting blocks



June 8, 1954 F. 5. FRlTZSCHE 2,680,697

ART OF CLEANSING LENS MOUNTING BLOCKS Filed March 4, 1953 IN V EN TOR.

A 770 IPA/5Y5.

Patented June 8, 1954 OFFICE ART. OF SING LENS M0UN TING BLOCK :FrcdFritzsche lvfilwaukee .Wis, assignor, .aby :mesneassignmenta'to 0. W.Coburn, Muskogee,

Okla.

ApplicatiomMarch '4, 1953, Serial No. 340,229

*6 Claims. 1

This invention relates generally to improvements in the art of cleaninglens mounting blocks, and relates more specificallyto :animproved methodof removing the pitch which is used to attach the blanks of opticallenses or "the like .to the blocks which support these/blanks while theyare being ground.

The primary object of my invention is to provide an improved method ofcleansing "lens mounting blocks :and for effectively removing pitchtherefrom after the finished lenses which were attached to the blocks bythe pitch during the lens grinding operation, have-been removed.

In the manufacture of 'optical'and other lenses, it is customary tofasten the lens blanks to mounting blocks by means of a heavy layer ofpitch deposited within'a cavity formed in one face of each of thecylindrical blocks. This pitch eifectively holds the blanks while theyare being ground and polished, and after the finished lenses have beenreleased the-pitch'must also be removed and the mounting blocks must bethoroughly cleaned preparatory to the applicationof fresh pitch layersand lens blanks. Many of these mounting blocks are provided with pitchinjection openings which become more or "less filled with plugs of pitchwhen the lens blanks are being fastened to the blocks,'-and after eachblank has been properly mounted upon a block thepitch hardens andadheres tofibot-h the blank and the block.

Inorder to clean the mounting blocks it has heretofore been commonpracticeto utilize a solution capable of dissolving the-pitch, whichbesides being'rather expensive, a-lsorequired a relatively long time.This solution furthermore became polluted and relatively'ineffectiveafter short usage, due to the absorption of the thick pitch layers; andwhen the blocks were "provided with injection opening containing plugsof the pitch, it was necessary to'knoc-k' these out withspecial tools.In some cases the excess pitch was also knocked ofi before the solventwas :used, butthis procedure aften resultedin damaging the mountingblocks, so that the prior cleaning methods weretedious, slow and costly.

It is therefore an important object ofthe present invention to. providean improved method of rapidly and effectively removing excess pitch fromlens mounting blocks and for prolonging the usefulness of pitch solventwhich'may be employed for final cleansing oft'he blocks.

Another important object of this invention is to provide a simplified;mode. of removin -pitch deposits from lens mounting ,zblocksw'ith theaid;

of heat butwithout danger of drawing the temper or otherwise marring theblocks, and without necessity of otherwise removing the plugs from thepitch injection openings with special equipment.

These and other more specific objects and advantages of the inventionwill be apparent from the following detailed description from which itwill be noted that the gist of the 1mprovement is the provision of amethod of corn fining a multiplicity of used metal lens mounting blockshaving concavities coated with. pitch, in inverted position upon aperforated deck, and for applying limited heat to the upper surfaces ofthe confined :bloclrs sufficient only to melt and cause .the pitch to\drip through the deck but insufficient to injure the finish of themetallic blocks.

A clear conception of the several steps involved in the improved method,and of the :construction and operation of a typical unit for exploitingthe method, may be had by referring to the drawingaccompanying andforming a part of thisspecification in which like reference charactersdesignate the same or similar parts in the various views.

Fig. l is .a perspective View of a commercial unit for effecting removalof excess pitch deposits from a group of lens mounting blocks, inaccordance with the improved method, showing the tray for holding theblocks only partially loaded and being removed from the heating :zone;

Fig. 2 is a somewhat enlarged vertical section through the unit of Fig.1, taken centrally through the heating zone and showing the heater inoperation;

.Fig. 3 is a further enlarged bottom view of a typical lens blankmounting block having a pitch injecting opening therethrough and itsconcavity lined with pitch which projects slightly beyond the blockperiphery; and

Fig.4 is a transverse section through an inverted mounting block such asshown in Fig. 3, the section being taken along the line 3-5.

While the invention has been shown and described as having beenexploited in an electrically heated unit for removing excess pitch fromcylindrical optical lens mounting blocks of a partie ular'type, it isnot my 'lntention to unnecessarily restrict the use ofthe method byvirtue of this limited showing; and it is also contemplated thatspecific descriptive terms usedherein be given the broadest possibleinterpretation consistentwith the disclosure.

- In accordance the improved method of removing the pitch from lensmounting blocks, and for finally cleaning the blocks preparatory to thereception of subsequent lens blanks, the used pitch lined blocks arefirst disposed in inverted position upon a perforated support, then theblock laden support is confined within a chamber which is heated onlysufficiently to melt the pitch and to cause most of the molten pitch togravitate from the heating zone through the support, and finally theblocks while still resting upon the support are immersed in a pitchsolvent solution which dissolves and removes the residual thin coatingof pitch from all sur faces and leaves the blocks in perfectly cleansedcondition.

A simple type of apparatus for carrying on the excess pitch removal, isillustrated in the drawing, and comprises in general, a table 6 having alarge central opening I and adapted to be supported upon legs 8; abasket 9 having an annular wall or brim provided with a carrying handleIll and with a perforated bottom deck II; an electrically energizedheating element I2 suspended from a top cover I3 having an annular rimor wall I4 adapted to cooperate with the brim of the basket 9 to providea confined heating zone I5 above the deck II; a lever I5 swingablysuspended from the table 5 by a pivot pin I? and being cooperable with adepending rod I8 secured to the cover I3 in order to lift the heaterwhile a block laden basket 9 is being applied to or removed from thetable 5; and means for energizing the heating element I2.

The table 6 may be formed of metal and the opening I should beunobstructed and of sufficient size to avoid overlapping the deck I Iwhen a basket 9 is resting upon the table top beneath the top cover I3,and the table supporting legs 8 should be of sufficient length to permita large sheet of cardboard I9 to be freely positioned between these legssome distance below the perforated deck I I. The circular baskets 9 ofwhich several duplicates may be provided, should also be formed ofdurable metal, and the annular brim of each basket should be slightlyhigher than the height of the mounting blocks 2i and of sufficientdiameter to accommodate at least several dozen of these blocks ZI. Theperforated block supporting deck II may be formed of screening or ofperforated sheet metal secured to the annular brim.

The electric heating element I2 is of spiral formation and is suspendedfrom the top cover I3 by means of clips 23 as shown in Fig. 2, and theannular rim I4 of the cover I3 should be formed to snugly fit the brimof each basket 9 When the latter are properly positioned upon the table6. The cover wall or rim I4 should also be of limited height in order tocause the heating element I2 to be located within the zone l5 closelyadjacent to but spaced slightly from the inverted blocks 2| restingwithin the baskets 9, and the cover i3 is provided with several parallelvertical guide pins 24 which are slidable through openings 25 in thetable =5 and cooperate with the lifting and lowering rod IE to maintainthe cover in horizontal position or parallel to the table top at alltimes. The heat ing element I2 is adapted to be controllably energizedfrom any suitable source of electric current through conductors 26extending through a ventilated housing 27 secured to the top of thecover I3; and the lever I6 has its medial portion fulcrumed upon the pinI! which coacts with a depending bracket 28 secured to the table 6,

while one end is swingable up and down to raise or lower the cover l3and its opposite end is provided with a manipulating handle 29.

The cylindrical lens mounting blocks 2| are accurately constructed ofsteel and are standard, and the base surface SI of each block is planeand provided with various types of block mounting detents 32, while theopposite surface 33 is of concave spherical zone formation and isconnected with the surface 5| by an opening 34.

. This opening 34 is utilized to inject fluent pitch 35 between theconcave surface 33 and each lens blank which is to be ground to shape,as shown in my prior Patent No. 2,465,153, granted March 22, 1949,entitled Apparatus for Blocking Optical Lens Blanks, and when the pitch35 has been injected it hardens and firmly retains the lens blank inposition upon the block 2| while the lens is being ground and finished.When each lens is finally ground and polished, it is removed from itsmounting block 25, leaving the surface 33 covered with an adhesive layerof pitch 35 which projects beyond the concavity and also partially fillsthe opening 36, as illustrated in Fig. 4, and the present improvedmethod and apparatus relate to the removal of this pitch so that theblocks 2i may be used for subsequent lens blank mounting purposes.

During commercial exploitation of the present improved method ofcleansing the pitch coated blocks 2i and after the finished lenses havebeen removed, a plurality of the blocks 2i are first placed in invertedposition upon the perforated bottom deck II of one of the baskets 9,whereupon the lever It should be manipulated as shown in Fig. 1 to liftthe cover I3 and the heating element I2 away from the table 5. The blockladen basket 33 may then be applied to the top of the table 8 beneathand in central alinement with the elevated cover I3, whereupon the covershould be lowered by gravity to position the parts as shown in Fig. 2with the rim I l of the cover I3 snugly engaging the brim of the basket9. The heating element I2 should thereafter be energized to graduallyheat the chamber I5 and the inverted blocks 2| confined therein,sufficient to melt the pitch 35 and to cause the excess molten pitch toflow through the perforations of the deck I I and to permit the pitch togravitate upon the cardboard I9 located beneath the table opening I.This heating should be continued until the bulk of the pitch 35 has beenremoved from the concave block surfaces 33 and from the openings 34 andonly a thin film of pitch remains, but must not be of sufiicientintensity to injure the finish of the blocks 2|.

When the excess pitch 35 has been thus removed, the heating element :2and cover I3 may again be elevated by manpulating the lever I6,whereupon the basket 9 can be withdrawn and immersed with the blocks 2Istill therein, within a bath of pitch solvent solution to quickly removethe residual thin pitch films and to thoroughly cleanse the blocks Eland the basket 9 as Well. These several cleansing steps may be carriedon in rapid succession; and in establishments wherein a great number oflenses are ground, several similar baskets 9 each adapted to hold threeor more dozens of inverted blocks 2I, may be provided. By properlyregulating the heat, scorching of the pitch 35 and resultant smoking andodors can be readily avoided; and since only a thin film of pitch needbe dissolved and removed by the solvent solution, the latter will remainpotent for a long period of time.

From the foregoing detailed description, it will be apparent that thepresent invention provides a simple but very eifective method ofcleaning the lens mounting blocks 2! and for preventing rapid pollutionof the costly solvent solution used for final cleansing of the blocks.When the cardboard sheets is have accumulated excessive deposits of thepitch 35, they may be discarded, and by enclosing the blocks 2| within aheating zone l5 in close proximity to the heating element i2 mostefficient heating results and the excess pitch is quickly removed. Thedegree of heating may also be regulated with simple controls so as toprevent smoking and odors, and the improved apparatus is simple, compactand readily manipulable to receive the successive blank laden baskets 9and to rapidly remove the major portion of the pitch deposits.

The use of the baskets 9 also facilitates handling and treatment oflarge numbers of the blanks 2! without necessity of touching theseblanks until they have been finally cleaned and dried, and the basketdeck I I is also cleaned While the blanks 21 are being immersed withinand swished through the final solution. The large opening 7 in the table6 prevents pitch from accumulating upon the table top, while the pins 24and the lifting rod 18 facilitate proper positioning of the successivebaskets l3 upon the table 6. The removal of the excess pitch 35 byheating also consumes far less time than when all of the pitch wasdissolved in a solvent solution as with the prior practice, besidesprolonging the usefulness of such solvent. The improved method andapparatus have proven highly satisfactory and successful in actual use,and may obviously be used in conjunction with various types of lensmounting blocks 2| whether provided with pitch injection openings 34 ornot.

It should be understood that it is not desired to limit this inventionto the exact steps of the method or to the precise construction of theapparatus, herein shown and described, because obvious modificationswithin the scope of the appended claims may occur to persons skilled inthe art.

I claim:

1. The method of cleansing pitch laden lens mounting blocks, whichcomprises, placing the blocks in inverted position upon a perforateddeck, gently heating the blocks to melt the excess pitch and to causethe molten pitch to gravitate through the erforations of the deck, andfinally immersing the blocks in a pitch solvent to remove the residualfilms of pitch therefrom.

2. The method of cleansing pitch laden lens mounting blocks, whichcomprises, placing the blocks in inverted position upon a perforated 6deck, gently heating the blocks to melt the excess pitch and to causethe molten pitch to gravitate through the perforations of the deck, andfinally immersing the blocks and the supporting deck in a pitch solventsolution to remove the residual films of pitch therefrom.

3. The method of cleansing pitch laden lens mounting blocks, whichcomprises, placing the blocks with their pitch laden surfaces restingupon a perforated deck, covering the deck and heating the covered blocksfrom above suflicient to melt the pitch and to cause excessive moltenpitch to escape through the deck perforations, and finally immersing theblocks in a patch solvent solution to remove residual pitch therefrom.

4. The method of cleansing pitch laden lens mounting blocks, whichcomprises, placing the blocks with their pitch laden surfaces restingupon a perforated deck, covering the deck and heating the covered blockfrom above sufficient to melt the pitch and to cause excessive moltenpitch to escape through the deck perforations, and finally immersing theblocks and their supporting deck in a pitch solvent solution to removeresidual pitch film therefrom.

5. The method of cleansing pitch laden lens mounting blocks, whichcomprises, placing the blocks en masse with their pitch ladenconcavities exposed directly toward a perforated supporting deck,enclosing the blocks from above and gently heating the same from aboveto melt the pitch and to cause excessive molten pitch to escape bygravity through the deck perforations, and thereafter exposing theblocks and deck to pitch solvent solution to remove residual pitchtherefrom.

6. The method of cleansing pitch laden lens mounting blocks having pitchinjection openings therein, which comprises, placing the blocks en massewith their pitch coated surfaces directed toward a. perforatedsupporting deck, enclosing the blocks and gently heating them from aboveonly sufficiently to melt excess pitch from within the injectionopenings and the pitch mounting surfaces of the blocks and to cause themolten pitch to escape through the deck perforations, and thereafterexposing the blocks to a pitch solvent to remove residual pitchtherefrom.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,596,214 OBrien Aug. 17, 1926 1,625,037 Lorenz Apr. 19, 19272,045,752 Butterworth June 30, 1936 2,105,767 Gettelman Jan. 18, 1938

1. THE METHOD OF CLEANSING PITCH LADEN LENS MOUNTING BLOCKS, WHICHCOMPRISES, PLACING THE BLOCKS IN INVERTED POSITION UPON A PERFORATEDDECK, GENTLY HEATING THE BLOCKS TO MELT THE EXCESS PITCH AND TO CAUSETHE MOLTEN PITCH TO GRAVITATE THROUGH THE PERFORATIONS OF THE DECK, ANDFINALLY IMMERSING THE BLOCKS IN A PITCH SOLVENT TO REMOVE THE RESIDUALFILMS OF PITCH THEREFROM.